Sql connection-string for localhost server

I am newbie in this .NET and please don't mind in answering my simple question. I am trying to write a windows application, where in I am using a localhost SQLserver for database.

I need to know what is the exact connection string for my localhost, if my server name looks like as below:

>> Data Source=HARIHARAN-PC\SQLEXPRESS;Initial Catalog=master;Integrated Security=True

should i need to give this same as connection string, or is something wrong in this syntax.

whn i try to open my connection. I am seeing error in opening connection.

How the format of connection string should be? any one please guide me.

I tried like this :

 private void button1_Click(object sender, EventArgs e)
    {
        string str = "Data Source=HARIHARAN-PC\SQLEXPRESS;Initial Catalog=master;Integrated Security=True" ; 
        SqlConnection con = new SqlConnection(str);
        SqlCommand cmd = new SqlCommand();
        SqlDataReader r;

        cmd.CommandText = "SELECT * from Table1";
        cmd.CommandType = CommandType.Text;
        cmd.Connection = con;

        con.Open();

        r = cmd.ExecuteReader();

        con.Close();
        
         
    }

This code errors out at con.Open();

Using the default instance (i.e., MSSQLSERVER, use the DOT (.))

<add name="CONNECTION_STRING_NAME" connectionString="Data Source=.;Initial Catalog=DATABASE_NAME;Integrated Security=True;" />

Choose a database name in Initial Catalog

Data Source=HARIHARAN-PC\SQLEXPRESS;Initial Catalog=your database name;Integrated Security=True" ;

see more

You can also use Dot(.) for local key i.e;

Data Source=.\SQLEXPRESS;Initial Catalog=master;Integrated Security=True

If you have the default server instance i.e. MSSQLSERVER, then just use dot for Data Source.

Data Source=.;Initial Catalog=master;Integrated Security=True

Do You have Internal Connection or External Connection. If you did Internal Connection then try this:

"Data Source=.\SQLEXPRESS;AttachDbFilename="Your PAth .mdf";Integrated Security=True;User Instance=True";

Try this connection string.

Data Source=HARIHARAN-PC\\SQLEXPRESS;Initial Catalog=yourDataBaseName;Integrated Security=True

See this link for more details http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.connectionstring%28v=vs.110%29.aspx

<add name="connstr" connectionString="Data Source=localhost;Initial Catalog=DBName;User Id=username;Password=password" providerName="System.Data.SqlClient"/>

The above also works. It ignores the username and password passed in in the connection string. I switched from an environment db to a local one, and it works fine even though my user in the connection string does not exist in this context.

In .Net configuration I would use something like:

"Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=..."

This information is from https://www.connectionstrings.com/sql-server-2016/

use this connection string :

Server=HARIHARAN-PC\SQLEXPRESS;Intial Catalog=persons;Integrated Security=True;

rename person with your database name

public string strConnectionstring = "Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\\DataBaseName.mdf";

string str = "Data Source=HARIHARAN-PC\\SQLEXPRESS;Initial Catalog=master;Integrated Security=True" ;

string str = @"Data Source=HARIHARAN-PC\SQLEXPRESS;Initial Catalog=master;Integrated Security=True" ;

When using SQL Express, you need to specify \SQLExpress instance in your connection string:

string str = "Data Source=HARIHARAN-PC\\SQLEXPRESS;Initial Catalog=master;Integrated Security=True" ;

Data Source=HARIHARAN-PC\SQLEXPRESS; Initial Catalog=Your_DataBase_name; Integrated Security=true/false; User ID=your_Username;Password=your_Password;

To know more about connection string Click here